I hate to be the bearer of bad news, but I'd be more inclined to just get the motor and controller here http://www.electricrider.com/ as the first upgrade most people usually make after getting a kit is to replace the marginal lead acid (which usually doesn't last long, total life wise) battery pack, with a better NiMiH pack, and that necessitates a compatible charger too, so almost right away that's half the cost of your kit.

A nice top of the line battery can be found here...

http://www.batteryspace.com/index.as...&Category=1272


Course, I know it gets pricey quick.